Five British soldiers were among the injured in the Basra bombings that have claimed the lives of nearly 70 people.
Basra has been seen as relatively peaceful
All five were members of the 1st Battalion Royal Welch Fusiliers, the Ministry of Defence later confirmed.
The men had left their barracks in Aldershot, Hampshire, earlier this month to begin operations.
The bombings outside police stations, which also killed children travelling in school buses, have raised concerns violence is spreading to south Iraq.
Prime Minister Tony Blair said the attackers were terrorists who aimed to prevent a "stable.. democratic Iraq".
Mr Blair said it was not necessary to send extra troops to UK-controlled southern Iraq but that the situation was always under review.
During prime minister's questions, he expressed his condolences "to
the families of those Iraqi people, including children, who were tragically
murdered in a series of explosions in Basra".
"Let us be clear that the majority of Iraqi people want a stable and democratic Iraq.
"These terrorists want to stop that and we, all of us, have to join with that majority in Iraq to see that terrorism does not succeed and democracy prevails."
The UK soldiers - one of whom was seriously wounded - are thought to have been hit at a police academy in Zubair, 25 km (16 miles) south of Basra.
All were from the Royal Welch Fusiliers, which recruits in Wales and has a home base in Aldershot.
The police academy attacked is thought to have been the one visited by Mr Blair during his New Year visit to southern Iraq.
During the visit, the prime minister met British police officers working to train Iraqi recruits.
UK Foreign Secretary Jack Straw described the attacks as "vicious" and said those responsible "care nothing for the people of Iraq".
"These vicious attacks were deliberately targeted on those Iraqis working hard to build a new future," he said.
Mr Straw had a message for terrorists: "We will not allow you to derail the process of transition to a sovereign and democratic Iraq.
"These are terrible people who are trying to deny the overwhelming majority of Iraqis a decent life and a democratic future."
Previously much of the worst violence in Iraq has been confined to Sunni areas of Iraq such as Baghdad and Falluja, under American control.
The academy attacked is thought to have been one visited by Tony Blair
Britain has suffered far fewer casualties, although recently soldiers have been injured in Amara.
A spokeswoman for the Ministry of Defence said: "Basra has been mainly calm, certainly whilst the trouble has been going on in Falluja. It is worrying."
Thomas Withington, a defence analyst and research associate at King's College
centre for defence studies, in London, said the developments were "deeply
He said: "This might indicate that the guerrilla war is widening to include the British sector as well."
Defence analyst Paul Beaver said the attacks were to demonstrate the fragile nature of British control.
"I see this as targeting the Iraqi police in order to demonstrate that the British are not as in control as people would like to believe.
"It is a demonstration... that the insurgents can still strike in an area where the British have been very successful in doing so many other things."
Mr Beaver said it was significant one of the attacks was in Zubair, an area he described as a "hot-bed" of Sunni resistance.